This invention relates to a support and positioner for a rock drill.
U.S. Pat. No. 3,185,222 in the name P. C. O'Leary dated May 25, 1965 describes an extendable and retractable mounting for rock drills having upper and lower air pressure cylinders pivotally connected on a base e.g. a jumbo. The piston of the lower cylinder which acts as a feed boom, carries at its free end a mounting on which a rock drill is pivotally secured. In operation, compressed air is admitted to the upper pressure cylinder which acts as a counterbalance for the weight of the rock drill and feed boom cylinder. This facilitates the positioning of the rock drill at a desired elevation, but it is still necessary for the drilling operative to manually lift the drill to the desired elevation. With the operative then holding the drill steady at the desired position and angle of attack, the operative opens a valve admitting air to the upwardly inclining feed boom cylinder, so this is extended, feeding the rock drill forwardly along an upwardly inclined line of action towards the rock face. As the operative guides the drill forwardly, the feed boom piston and cylinder are swung progressively downwardly by hand, in order to compensate for the upward component of the motion of the feed boom piston as it progressively advances towards an extended position, in order to maintain the advance of the drill bit along a predetermined horizontal line of advance.